Method and article for deterring theft of returnable containers

ABSTRACT

A reusable plastic container for delivery products, such as a dairy crate, a bakery tray, a beverage crate or a produce tray, is formed of a composition including a plastic resin and an electrically conductive or magnetic material distributed substantially uniformly throughout the plastic resin. The electrically conductive or magnetic material can be carbonyl iron powder in an amount between about 0.25% and about 2.0% of the composition by weight. The powder is distributed throughout the container and is detectable by an electromagnetic detection apparatus for screening plastic materials for regrinding. The container has a notice affixed to it, which indicates that the container includes the electrically conductive or magnetic material and that discourages regrinding of the container.

BACKGROUND

This invention relates to molded plastic containers. More particularly, it relates to molded plastic returnable containers for transporting delivery products, such as dairy products, beverages, baked goods, produce and the like.

Dairies typically deliver their product in plastic crates. These crates are left with customers, and the empty crates are picked up when the next delivery occurs. Plastic bakery trays, beverage crates or holders, and other products are used in a similar fashion. These crates and trays are subject to loss. Customers of products delivered in such crates and trays often are required to purchase additional crates or trays due to such loss, including theft. Typically, customers purchase more crates and trays due to loss than due to wear. Frequently, crates and trays that are not returned have been stolen and are illegally salvaged for their plastic, which is reground to be recycled.

It is an object of this invention, therefore, to provide a plastic container that can deter its theft.

Additional objects and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations pointed out in the appended claims.

SUMMARY

To achieve the foregoing objects, and in accordance with the purposes of the invention as embodied and broadly described in this document, there is provided a reusable plastic container for delivery products. By way of example, the container can be in the form of a dairy crate, a bakery tray, a beverage crate or a produce tray. The container includes a frame formed of a composition including a plastic resin and an electrically conductive or magnetic material distributed substantially uniformly throughout the plastic resin. The electrically conductive or magnetic material is in an amount sufficient to trigger a metal detector alarm. Typically, the electrically conductive or magnetic material is between about 0.25% and about 2.0% of the composition by weight. In one advantageous embodiment, the electrically conductive or magnetic material is about 1.0% by weight. Preferably, the container has a notice affixed to it, which indicates that the container includes the electrically conductive or magnetic material and that discourages regrinding of the container.

A method for manufacturing a reusable plastic container for delivery products according to the present invention is also provided. The method includes: providing a thermoplastic resin; mixing particles of an electrically conductive or magnetic material with the thermoplastic resin; heating the thermoplastic resin to plasticize the thermoplastic resin for molding; and molding the heated thermoplastic resin and the particles of an electrically conductive or magnetic material into a container suitable for transporting a delivery product. The particles of electrically conductive or magnetic material can be mixed with the thermoplastic resin before heating the thermoplastic resin. Mixing the metal additive with the thermoplastic resin can include adding the particles of electrically conductive or magnetic material to a coloring agent to produce a coloring mixture and mixing the coloring mixture with the thermoplastic resin. According to one advantageous method of manufacturing a reusable container according to the invention, the electrically conductive or magnetic material comprises a powder, such as carbonyl iron powder.

A method of providing a returnable plastic container for delivery products, according to the invention, includes providing a container comprising an organic plastic and particles that are detectable by an electromagnetic detection apparatus for screening plastic materials for regrinding. The particles are positioned and proportioned such that the container may easily be detected by the electromagnetic detection apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate the presently preferred embodiments of the invention and, together with the general description given above and the detailed description of the preferred methods and embodiments given below, serve to explain the principles of the invention.

FIG. 1 is a perspective view of one embodiment of a dairy crate according to the present invention.

FIG. 2 is a schematic diagram of a process for manufacturing the container of FIG. 1.

DESCRIPTION

Reference will now be made in more detail to the presently preferred methods and embodiments of the invention, as illustrated in the accompanying drawings, in which like numerals refer to like parts throughout the several views. While the invention will be described more fully with reference to these examples and drawings, the invention in its broader aspects is not limited to the specific details, representative devices, and illustrative examples shown and described. Rather, the description which follows is to be understood as a broad, teaching disclosure directed to persons of ordinary skill in the appropriate arts, and not as limiting upon the invention.

The invention is directed to a plastic container for delivery products, such as a plastic beverage delivery crate, which has particles of electrically conductive or magnetic material embedded in the plastic and secured integrally with the container. Adding such particles of material to the plastic container serves to deter the theft of the container by those who sell such containers to recyclers for the salvage value of the recycled plastic. The conductive or magnetic particles are provided in a sufficient amount to activate a metal detector typically used on a recycling grinder conveyer. This activation of the metal detector will automatically shut down the conveyer belt feeder and will thereby deter regrinding of the container. In addition, the level and distribution of the conductive or magnetic particles within the container make salvage of a pure form of the plastic used for the container difficult to achieve, thereby diminishing this crate's salvage resale value. Both of these features deter the theft and illegal salvage of the plastic crate.

Referring to FIG. 1, a container 10 has a base 12 and peripheral walls 14, 16, 18, 20. The crate 10 is formed of a composition including a moldable plastic resin and particles embedded within the plastic resin, which particles are of a material that is detectable by a detector used by regrinders to detect foreign material in recycled plastic materials. Preferably, the particles are distributed throughout the plastic container. The particles may be molded with the plastic in forming the container, whether or not uniformly dispersed throughout the container. The particles are provided in an amount sufficient to trigger the detector alarm. Affixed to the container is a notice 22, which indicates that the container includes a non-plastic material and that discourages regrinding of the container. Although the container shown in FIG. 1 is a dairy crate, it will be understood that the invention can be utilized for other plastic returnable items that are susceptible to theft and illegal regrinding, including beverage delivery crates, bakery trays, produce trays and the like.

Suitable plastic resins for forming the container 10 include thermoplastics, such as high density polyethylene (HDPE) or polypropylene, although other moldable organic resin polymers are satisfactory if the molded container has satisfactory strength. A suitable material for the particles 32 is an iron powder. In a presently preferred embodiment, the particles 32 are provided in the form of a ferrous metal powder such as that normally used for powdered metallurgy. One such powder is Carbonyl Iron Powder OM (Material #50054704) available from BASF Corporation, which has North American headquarters in Florham Park, N.J. This is a mechanically hard powder typically having iron content greater than 97.8% and particle size in a range from about 2 82 m to about 9 μm. The carbonyl iron powder is included in the thermoplastic container an amount from about 0.25% to about 2.0% of the composition by weight. In one advantageous embodiment, the metal particles are about 1.0% by weight. Upon reading this specification, those of skill in the art will understand that other suitable materials may be used for the particles 32, giving consideration to such matters as the electrical and magnetic properties of the material, the type of detectors used by regrinders, wear on the equipment used to manufacture the containers, and the like.

According to one preferred method of manufacture, the container 10 with embedded particles is made using an injection molding process to form a thermoplastic material. FIG. 2 shows a schematic diagram for this manufacturing process. Referring to FIG. 2, a supply of moldable plastic 30, usually in the form of pellets, is mixed with electrically conductive or magnetic particles 32. As discussed above, suitable thermoplastics include high density polyethylene (HDPE) and polypropylene. The particles 32 preferably are a ferrous metal, but also can be non-ferrous particles so long as the particles can be distributed and proportioned within the container such that the container will be detected by a metal detector used to scan plastic articles before regrinding.

Referring again to FIG. 2, the conductive or magnetic particles 32 are mixed with a liquid color 34 typically used to color molded thermoplastic (step 100). The mixture of liquid color 34 and particles 32 is then is metered into an injection molding machine, to be combined with the plastic (step 102). The combination of plastic 30 and the mixture of liquid color 34 and particles 32 is then melted and blended into a substantially homogeneous mixture as it is melted (step 104). This can be achieved using a conventional injection molding mixer of the type for blending dyes or pigments or fillers before injection molding. The molten mixture is then fed from mixer to an injection mold (step 106) where it is molded into a container 10 with the magnetic particles distributed substantially uniformly throughout the container (step 108). Injection molds are commercially available and are well known in the art.

Upon reading this specification, those of knowledge in the art will understand that other methods may be used for mixing the conductive or magnetic particles with the plastic. For example, the carbonyl iron powder may be added by other means that do not require mixing the powder with a liquid color, such as via a direct powder feeder.

Using the method described above, I have manufactured containers using HDPE pellets and carbonyl iron powder in varying amounts to determine a suitable mixture to activate the alarm of a metal detector such as that typically used by a regrinder. The completed containers were run through a metal detector to determine the amount of material required to activate the alarm. Favorable results have been achieved using about 1% carbonyl iron powder by weight. Additional examples are set forth below.

EXAMPLES

The following examples help to further explain the invention. It will be understood, however, that the examples are illustrative of the invention and that the invention is not limited only to these examples. For each of the examples, a model Metron C metal detector from Bunting Magnetics Co. of Newton, Kan. was used to test the exemplary containers.

Example 1

The metal detector was set at 50% sensitivity and a container having a composition of HDPE and 0.25% carbonyl iron powder by weight did not trigger the alarm.

Example 2

Using the container of Example 1, the sensitivity of the metal detector was increased to 66%. The container composed of HDPE and 0.25% carbonyl iron powder by weight then triggered the alarm.

Example 3

The metal detector was set at 50% sensitivity. A container having a composition of HDPE and 0.5% carbonyl iron powder by weight triggered the alarm.

Example 4

The metal detector was set at 50% sensitivity. A container having a composition of HDPE and 0.75% carbonyl iron powder by weight triggered the alarm.

Example 5

The metal detector was set at 50% sensitivity. A container having a composition of HDPE and 1.0% carbonyl iron powder by weight triggered the alarm.

The normal operating level for a metal detector like that used for screening plastic materials for regrinding is typically 80% sensitivity. 100% sensitivity is generally too sensitive for normal use. Our examples show that a container composed of HDPE and 0.25% carbonyl iron powder by weight is adequate to trigger the metal detector at 80% sensitivity. A composition of HDPE and carbonyl iron powder in a range from about 0.5% to 1.0% by weight, however, provides some margin to account for operators that might set their systems to a sensitivity level below 80%.

From the foregoing disclosure, it will be understood by those having skill in the art that the present invention can have additional advantages and modifications. Therefore, the invention in its broader aspects is not limited to the specific details, representative devices, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the general inventive concept. 

1. A reusable plastic container for delivery products, the container comprising: a container adapted for holding a delivery product, wherein the container comprises a frame formed of a composition comprising a plastic resin and particles of an electrically conductive or magnetic material distributed substantially uniformly throughout the plastic resin.
 2. The container of claim 1 wherein the particles of electrically conductive or magnetic material are greater than about 0.25% of the composition by weight.
 3. The container of claim 1 wherein the particles of electrically conductive or magnetic material are between about 0.25% and about 2.0% of the composition by weight.
 4. The container of claim 1 wherein the particles of electrically conductive or magnetic material are in an amount sufficient to trigger a metal detector alarm.
 5. The container of claim 1 wherein the container comprises a dairy crate.
 6. The container of claim 1 wherein the container comprises a bakery tray.
 7. The container of claim 1 wherein the container comprises a beverage crate.
 8. The container of claim 1 wherein the container comprises a produce tray.
 9. The container of claim 1 further comprising a notice affixed to the container, wherein the notice indicates that the container includes the electrically conductive or magnetic material.
 10. A method for manufacturing a reusable plastic container for delivery products, the method comprising: providing a thermoplastic resin; mixing an electrically conductive or magnetic material with the thermoplastic resin; heating the thermoplastic resin to plasticize the thermoplastic resin for molding; molding the heated thermoplastic resin and the electrically conductive or magnetic material into a container suitable for transporting a delivery product.
 11. The method of claim 11 wherein the electrically conductive or magnetic material is mixed with the thermoplastic resin before heating the thermoplastic resin.
 12. The method of claim 11 wherein: mixing the electrically conductive or magnetic material with the thermoplastic resin comprises adding the electrically conductive or magnetic material to a coloring agent to produce a coloring mixture; and mixing the coloring mixture with the thermoplastic resin.
 13. The method of claim 11 wherein the electrically conductive or magnetic material comprises a powder.
 14. The method of claim 14 wherein the powder comprises a carbonyl iron powder.
 15. A method for providing a delivery product in a reusable container, the method comprising: delivering the delivery product in a container formed of a composition comprising a thermoplastic resin and an electrically conductive or magnetic material.
 16. The method of claim 16 wherein the electrically conductive or magnetic material comprises a powder.
 17. The method of claim 16 wherein the powder comprises a carbonyl iron powder.
 18. The method of claim 16 wherein the electrically conductive or magnetic material is in an amount sufficient to trigger a metal detector alarm.
 19. The method of claim 16 wherein the electrically conductive or magnetic material is greater than about 0.25% of the composition by weight.
 20. The method of claim 16 wherein the electrically conductive or magnetic material is between about 0.25% and about 2.0% of the composition by weight.
 21. The method of claim 16 wherein the container comprises a dairy crate.
 22. The method of claim 16 wherein the container comprises a bakery tray.
 23. The method of claim 16 wherein the container comprises a beverage crate.
 24. The method of claim 16 wherein the container comprises a produce tray.
 25. The method of claim 16 further comprising affixing to the container a notice that the container includes the electrically conductive or magnetic material.
 26. The method of claim 16 further comprising affixing to the container a notice discouraging regrinding of the container.
 27. A method of producing a returnable plastic container for delivery products, the method comprising: providing an organic plastic for molding; providing particles of an electrically conductive or magnetic material; mixing the particles of electrically conductive or magnetic material with the organic plastic; heating the mixture of organic plastic and particles of electrically conductive or magnetic material; and molding the heated mixture of organic plastic and particles of electrically conductive or magnetic material to produce a container for delivery products having the particles of electrically conductive or magnetic material distributed and proportioned such that the container will be detected by a metal detector for scanning plastic articles before regrinding.
 28. A method of providing a returnable plastic container for delivery products, the method comprising: providing an container comprising an organic plastic and particles that are detectable by an electromagnetic detection apparatus for screening plastic materials for regrinding, wherein the particles are positioned and proportioned such that the container may easily be detected by the electromagnetic detection apparatus. 